The present invention I relates to a novel polypropylene block copolymer, which has a high molecular weight and comprises polypropylene-b-poly(ethylene-co-propylene) including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked.
The present invention II relates to a blushing-resistant transparent polypropylene resin for molding, comprising a novel polypropylene block copolymer, polypropylene-b-poly(ethylene-co-propylene), including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked, and to molded articles obtained therefrom. The molded articles exhibit excellent transparency and blushing resistance, as well as well-balanced tensile strength, tensile elongation, impact resistance at low temperature, and heat resistance.
The present invention III relates to an elastomer for molding, comprising a novel polypropylene block copolymer, polypropylene-b-poly(ethylene-co-propylene), including a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked. Molded articles obtained therefrom exhibit excellent transparency, blushing resistance, and flexibility and have excellent impact resistance, mechanical strength, and appearance.
Today, polypropylene resins, which are comparatively inexpensive and exhibit excellent thermal and mechanical strength, are used in a variety of fields. Propylene homopolymers generally have high rigidity, but have poor transparency, impact resistance, and particularly, poor impact resistance at low temperatures.
Propylene-xcex1-olefin random copolymers, which are produced by copolymerizing propylene and a small amount of xcex1-olefin so as to enhance transparency of propylene homopolymers, are widely employed in a variety of industrial fields, beginning with in domestic electric appliances and articles for daily use. These conventionally employed propylene random copolymers have excellent transparency. However, these copolymers have poor impact resistance as compared with propylene homopolymers and have considerably low heat resistance, imposing a limitation on the temperature at which they are used. Thus, the field of use of these copolymers is limited.
In order to enhance impact resistance of propylene homopolymers at low temperatures, propylene block copolymers, which are produced by forming a propylene homopolymer component and, subsequently forming an ethylene-propylene random copolymer, are widely employed in a variety industrial fields, beginning with in automobiles and domestic electric appliances and articles for daily use.
These conventionally employed propylene block copolymers have excellent impact resistance, but have considerably poor transparency as compared with propylene homopolymers. Thus, the block copolymers undergo severe blushing under impact.
In order to overcome undesirable impact-induced-blushing of these propylene block copolymers, there have been proposed a method involving increasing the ethylene content of a copolymer and a method involving addition of polyethylene to a propylene block copolymer. These two methods are excellent in view of mitigation of impact-induced-blushing; however, the transparency of molded articles decreases.
In addition, Japanese Patent Application Laid-Open (kokai) No. 5-331327 discloses a polymer composition in which only the ratio of intrinsic viscosity of the propylene homopolymer component to that of the ethylene-propylene random copolymer component is specified in a propylene block copolymer and, Japanese Patent Application Laid-Open (kokai) No. 6-145268 discloses a polymer composition in which the ratio of intrinsic viscosity of the propylene homopolymer component to that of the ethylene-propylene random copolymer component and the ethylene content of the ethylene-propylene random copolymer component are both specified.
However, when injection-molded articles of the aforementioned polymer composition were tested for properties including impact resistance, blushing, and haze (which is an index of transparency), it was found that these properties were improved as compared with conventional propylene block copolymer, but that the degree of improvement was still unsatisfactory.
As described in Japanese Patent Application Laid-Open (kokai) Nos. 56-72042 and 57-63350 discloses a polyolefin resin compositions formed by blending an ethylene-propylene copolymer containing a small amount of ethylene with an ethylene-propylene block copolymer. However, the resin composition has drawbacks; e.g., an economical disadvantage due to the requirement for a blending step and a decrease in performance of final products due to poor dispersion of components.
Japanese Patent Application Laid-Open (kokai) Nos. 8-92338 and 9-87343 disclose a polypropylene-b-poly(ethylene-co-propylene) comprising a polypropylene segment and a poly(ethylene-co-propylene) segment, with the two types of segments being chemically linked, and a method of-producing the same. Specifically: disclosed therein are block copolymers having a number-average molecular weight (Mn) of 11,000-20,000; a molecular weight distribution index (weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of 3.3-3.8; and an ethylene content of 26 mol %.
However, such polymers having a low weight-average molecular weight are not suitable for producing general-purpose molded articles.
Japanese Patent Application Laid-Open (kokai) No. 9-241334 discloses a block copolymer having an intrinsic viscosity [xcex7] of 0.8, a block copolymer segment content of 34 wt. %, and an ethylene content of the block copolymer segment of 40 wt. %.
However, the polymer disclosed therein also has a weight-average molecular weight of as low as approximately 80,000, and thus, it is not suitable for producing general-purpose molded articles.
In addition, there have conventionally been known polyolefin thermoplastic elastomers produced by incorporating, into a polypropylene polymer, an amorphous ethylene-xcex1-olefin random copolymer or by incorporating, into a polypropylene polymer, a hydrogenated product of a styrene-butadiene block copolymer. These elastomers are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 50-14742, 52-65551, 58-206644, and 58-215446.
However, the elastomer compositions produced by incorporating, into a polypropylene copolymer, a hydrogenated product of a styrene-butadiene block copolymer and hydrocarbon oil for improving flowability provide molded articles having a disadvantageously decreased mechanical strength (tensile strength and bending strength). Although the elastomer compositions produced by incorporating, into a polypropylene polymer, an amorphous thylene-xcex1-olefin random copolymer have good rubber elasticity, the compositions disadvantageously exhibit poor mold-releasability during molding thereof and, if the amorphous ethylene-xcex1-olefin random copolymer content is high, even no mold-releasability at all.
Japanese Patent Application Laid-Open (kokai) No. 61-14248 discloses an elastomer composition produced by incorporating, into a propylene-ethylene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer and, optionally, an amorphous ethylene-propylene rubber.
However, the above elastomer composition still have a problem in that it provides molded articles with a defective appearance due to, e.g., flow marking on the surfaces of produced articles.
The elastomer composition produced by adding optional amorphous ethylene-propylene rubber to a mixture of a propylene homopolymer and the aforementioned hydrogenated product of a styrene-butadiene block copolymer cannot attain favorable rubber elasticity and has an insufficient impact resistance at low temperatures. Although a similar elastomer composition employing a propylene-ethylene random copolymer instead of the aforementioned propylene homopolymer provides molded articles having excellent mechanical strength, impact resistance, and appearance, sink marks and fins are prone to be generated on the articles, thereby disadvantageously lowering moldability.
Japanese Patent Application Laid-Open (kokai) No. 5-1817 discloses a composition for solving the aforementioned problems. Specifically, the composition is produced by incorporating, into a polypropylene copolymer comprising a propylene-ethylene block copolymer and a crystalline propylene-ethylene random copolymer, a hydrogenated product of styrene-butadiene block copolymer.
As described above, specific amounts of a variety of copolymers have been incorporated into elastomer compositions in order to solve the problems unique to such elastomers. However, since the thus-produced elastomer compositions are provided in the form of mixtures, dispersion of components is poor and not homogeneous, and articles having excellent transparency and blushing resistance have never been produced from such compositions.
Japanese Patent Application Laid-Open (kokai) No. 8-269258 discloses a composition for producing a transparent and blushing-resistant elastomer composition. Specifically, the composition is produced by incorporating, into a polypropylene copolymer, an ethylene-xcex1-olefin copolymer elastomer having a limited composition. However, in this case also, the composition has drawbacks; e.g., an economical disadvantage due to the requirement for a blending step and a decrease in performance of final products due to poor dispersion of components.
In view of the foregoing, an object of the present invention I is to provide a propylene-ethylene block copolymer which has a weight-average molecular weight of 100,000 or more; is suitable for producing general-purpose molded articles; and has well-balanced mechanical properties, impact resistance, thermal properties, transparency, moldability, and other properties.
As described above, the conventional ethylene-propylene block copolymers cannot fully attain the target properties, since a polypropylene segment and a poly(ethylene-co-propylene) segment are linked not chemically. Thus, an object of the present invention II is to provide a blushing-resistant transparent polypropylene resin for molding, which resin exhibits further enhanced transparency and blushing resistance and has well-balanced tensile strength, tensile elongation, impact resistance, and thermal properties. Another object of Invention II is to provide molded articles obtained therefrom.
Further, an object of the present invention III is to provide a polypropylene elastomer for molding, which elastomer, when employed alone, can provide molded articles exhibiting excellent transparency, blushing resistance, and flexibility and have excellent impact resistance and mechanical strength.
Regarding the present invention I, the present inventors have conducted extensive studies on the factors affecting physical properties and moldability of propylene-ethylene block copolymers, and have found that, in contrast to a block copolymer according to the conventional technique in which polypropylene and poly(ethylene-co-propylene) are present in a blended state, the propylene-ethylene block copolymer of the present invention is a copolymer containing a genuine block copolymer as defined in polymer chemistry in which the polypropylene segments and the poly(ethylene-co-propylene) segments are linked via a chemical bond; having a sufficiently large weight-average molecular weight; capable of providing general-purpose molded articles through molding; and providing molded articles with well-balanced mechanical properties, impact resistance, thermal properties, transparency, and physical properties during processing, etc. The present invention I has been accomplished on the basis of these findings.
Accordingly, Invention I-1 provides a propylene-ethylene block copolymer containing polypropylene-b-poly(ethylene-co-propylene), characterized by having a weight-average molecular weight (Mw) of the propylene-ethylene block copolymer of 100,000 or more; a poly(ethylene-co-propylene) segment content of not less than 5 wt. % and less than 100 wt. %; and a total ethylene content of 2-95 wt. %, wherein the propylene-ethylene block copolymer has the following characteristics (a) and (b):
(a) polypropylene segments and poly(ethylene-co-propylene) segments are linked chemically; and
(b) the polypropylene segments and poly(ethylene-co-propylene) segments are synthesized in the presence of an olefin polymerization catalyst comprising an organometallic compound and a solid catalyst component comprising either titanium and a halogen or titanium, magnesium, and a halogen.
Invention I-2 provides a propylene-ethylene block copolymer as described in Invention I-1, wherein the propylene-ethylene block copolymer has a molecular weight distribution index (weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of 3.5 or more.
Invention I-3 provides a propylene-ethylene block copolymer as described in Invention I-1 or I-2, wherein the propylene-ethylene block copolymer contains a xylene-soluble component during extraction by use of xylene at 20xc2x0 C. in an amount of 50 wt. % or less.
Invention I-4 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-3, wherein the ratio of the poly(ethylene-co-propylene) segments remaining after extraction by use of xylene at 20xc2x0 C. to the segments before extraction is 50 wt. % or more.
Invention I-5 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-4, wherein the ratio of the total ethylene content remaining after extraction by use of xylene at 20xc2x0 C. to the content before extraction is 50 wt. % or more.
Invention I-6 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-5, wherein the propylene-ethylene block copolymer has an elution-completion temperature in cross-fractionation chromatography of 100-120xc2x0 C.
Invention I-7 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-6, wherein the propylene-ethylene block copolymer has a melting point (Tm) of 135xc2x0 C. or higher.
Invention I-8 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-7, wherein the propylene-ethylene block copolymer exhibits a melt tension at 190xc2x0 C. of 1.0 g or more.
Invention I-9 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-8, wherein the peak temperature of complex modulus loss tangent ID (tan xcex4) based on glass transition temperature of the PP portion of the propylene-ethylene block copolymer falls within the range of xe2x88x9250xc2x0 C. to 10xc2x0 C.
Invention I-10 provides a propylene-ethylene block copolymer as described in any one of Inventions I-1 to I-9, wherein the propylene-ethylene block copolymer exhibits a storage modulus (Exe2x80x2) at 150xc2x0 C. of (0.1-30)xc3x97107 dyne/cm2.
Invention I-11 provides a propylene-ethylene block copolymer containing polypropylene-b-poly(ethylene-co-propylene), characterized in that the weight-average molecular weight (Mw) of the propylene-ethylene block copolymer is 100,000 or more; the poly(ethylene-co-propylene) segment content is not less than 5 wt. % and less than 100 wt. %; the total ethylene content is 2-95 wt. %; the molecular weight distribution index (weight-average molecular weight (Mw)/number-average molecular weight (Mn)) is 3.5 or more; the propylene-ethylene block copolymer contains a xylene-soluble component during extraction by use of xylene at 20xc2x0 C. in an amount of 50 wt. % or less; and the ratio of the poly(ethylene-co-propylene) segments remaining after extraction by use of xylene at 20xc2x0 C. to the segments before extraction is 50 wt. % or more.
Invention I-12 provides a propylene-ethylene block copolymer as described in Invention I-11, wherein the ratio of the total ethylene content remaining after extraction by use of xylene at 20xc2x0 C. to the content before extraction is 50 wt. % or more.
Invention I-13 provides a propylene-ethylene block copolymer as described in Invention I-11 or I-12, wherein the propylene-ethylene block copolymer has an elution-completion temperature in cross-fractionation chromatography of 100-120xc2x0 C.
Invention I-14 provides a propylene-ethylene block copolymer as described in any one of Inventions I-11 to I-13, wherein the propylene-ethylene block copolymer has a melting point (Tm) of 135xc2x0 C. or higher.
Invention I-15 provides a propylene-ethylene block copolymer as described in any one of Inventions I-11 to I-14, wherein the propylene-ethylene block copolymer exhibits a melt tension at 190xc2x0 C. of 1.0 g or more.
Invention I-16 provides a propylene-ethylene block copolymer as described in any one of Inventions I-11 to I-15, wherein the peak temperature of complex modulus loss tangent (tan xcex4) based on a glass transition temperature of the PP portion of the propylene-ethylene block copolymer falls within the range of xe2x88x9250xc2x0 C. to 10xc2x0 C.
Invention I-17 provides a propylene-ethylene block copolymer as described in any one of Inventions I-11 to I-16, wherein the propylene-ethylene block copolymer exhibits a storage modulus (Exe2x80x2) at 150xc2x0 C. of (0.1-30)xc3x97107 dyne/cm2.
Regarding the present invention II, the present inventors have conducted extensive studies on the factors affecting transparency, blushing resistance, tensile elongation, and heat resistance of propylene-ethylene block copolymers, and have found that, in contrast to block copolymer according to the conventional technique in which polypropylene and poly(ethylene-co-propylene) are present in a blended state, the blushing-resistant transparent polypropylene resin for molding of the present invention is a copolymer containing a genuine block copolymer as defined in polymer chemistry in which the polypropylene segments and the poly(ethylene-co-propylene) segments are linked via a chemical bond, and can improve transparency, blushing resistance, tensile strength, tensile elongation, and heat resistance by solo use thereof. Invention II has been accomplished on the basis of these findings.
Accordingly, Invention II-1 provides a blushing-resistant transparent polypropylene resin for molding containing polypropylene-b-poly(ethylene-co-propylene), characterized by having a poly(ethylene-co-propylene) segment content of polypropylene-b-poly(ethylene-co-propylene) of not less than 5 wt. % and less than 50 wt. % and a total ethylene content of polypropylene-b-poly(ethylene-co-propylene) of 0.25-47 wt. %, wherein the polypropylene-b-poly(ethylene-co-propylene) has the following characteristics (a) and (b)
(a) polypropylene segments and poly(ethylene-co-propylene) segments are linked chemically; and
(b) the polypropylene segments are synthesized in the presence of an olefin polymerization catalyst comprising an organometallic compound and a solid catalyst component comprising either titanium and a halogen or titanium, magnesium, and a halogen, and subsequently, the poly(ethylene-co-propylene) segments are synthesized.
Invention II-2 provides a blushing-resistant transparent polypropylene resin for molding as described in Invention II-1, wherein the polypropylene-b-poly(ethylene-co-propylene) has a weight-average molecular weight (Mw) of 30,000 or more.
Invention II-3 provides a blushing-resistant transparent polypropylene resin for molding as described in Invention II-1 or II-2, wherein the polypropylene-b-poly(ethylene-co-propylene) has a molecular weight distribution index (weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of 3.5 or more.
Invention II-4 provides a blushing-resistant transparent polypropylene resin for molding as described in any one of Inventions II-1 to II-3, wherein the polypropylene-b-poly(ethylene-co-propylene) contains a component soluble in xylene at 20xc2x0 C. in an amount of 50 wt. % or less.
Invention II-5 provides a blushing-resistant transparent polypropylene resin for molding as described in any one of Inventions II-1 to II-4, wherein the polypropylene-b-poly(ethylene-co-propylene) has a melting point (Tm) of 135xc2x0 C. or higher.
Invention II-6 provides a blushing-resistant transparent polypropylene molded article formed by molding a blushing-resistant transparent polypropylene resin for molding as recited in any one of Inventions II-1 to II-5.
Invention II-7 provides a blushing-resistant transparent polypropylene molded article as described in Invention II-6, wherein molding is carried out through injection molding.
Regarding the present invention III, the present inventors have conducted extensive studies in order to solve the aforementioned problems of polypropylene elastomer compositions, and have found that, in contrast to conventional block copolymers in which polypropylene and poly(ethylene-co-propylene) are present in a blended state, the elastomer for molding of the present invention is a copolymer containing a genuine block copolymer as defined in polymer chemistry in which the polypropylene segments and the poly(ethylene-co-propylene) segments are linked via a chemical bond, and can solve the problems by solo use thereof and without adding an elastomer such as a hydrogenated product of a styrene-butadiene block copolymer or an ethylene-xcex1-olefin copolymer. Invention III has been accomplished on the basis of these findings.
Accordingly, Invention III-1 provides an elastomer for molding containing polypropylene-b-poly(ethylene-co-propylene), characterized by having a poly(ethylene-co-propylene) segment content of polypropylene-b-poly(ethylene-co-propylene) of 50-95 wt. % and a total ethylene content of polypropylene-b-poly(ethylene-co-propylene) of 2.5-95 wt. %, wherein the polypropylene-b-poly(ethylene-co-propylene) has the following characteristics (a) and (b):
(a) polypropylene segments and poly(ethylene-co-propylene) segments are linked chemically; and
(b) the polypropylene segments are synthesized in the presence of an olefin polymerization catalyst comprising an organometallic compound and a solid catalyst component comprising either titanium and a halogen or titanium, magnesium, and a halogen, and subsequently, the poly(ethylene-co-propylene) segments are synthesized.
Invention III-2 provides an elastomer for molding as described in Invention III-1, wherein the polypropylene-b-poly(ethylene-co-propylene) has a weight-average molecular weight (Mw) of 30,000 or more.
Invention III-3 provides an elastomer for molding as described in Invention III-1 or III-2, wherein the polypropylene-b-poly(ethylene-co-propylene) has a molecular weight distribution index (weight-average molecular weight (Mw)/number-average molecular weight (Mn)) of 3.5 or more.
Invention III-4 provides an elastomer for molding as described in any one of Inventions III-1 to III-3, wherein the polypropylene-b-poly(ethylene-co-propylene) contains a component soluble in xylene at 20xc2x0 C. in an amount of 50 wt. % or less.
Invention III-5 provides an elastomer for molding as described in any one of Inventions III-1 to III-4, wherein the polypropylene-b-poly(ethylene-co-propylene) has a melting point (Tm) of 135xc2x0 C. or higher.
Invention III-6 provides an elastomer-molded article formed by molding an elastomer for molding as recited in any one of Inventions III-1 to III-5.
Invention III-7 provides an elastomer-molded article as described in Invention III-6, wherein molding is carried out through injection molding.